Pickling solution



UNITED STATES 1&

PATENT OFFICE PICKLING SOLUTION Stephen F. Urban, Chicago, 11!.

No Drawing. Application October 7, 1937, Serial No. 167,859

1 Claim. (01. ilk-a) This invention relates tmniflklinwlutions and, particularly, to such a solution for pickling chro- 5 In the course of manufacture of chromium steel alloy or chromium-nickel steel alloy articles, sheets, etc., a scale is formed on the surface thereof. This scale has to be removed for various reasons before such articles can be used commercially. As is generally known, it is the usual practice to re movelhemcalg by immersing the articles in a pickling solutiomafte'i me final annealing operation: -It s an object of this invention to provide a l pickling solution which will remove this scale n'from such metals without pit 'ng gqr ip dj ng otherwise da theof.

It has been found that annealed chrome steels m r,w or hsutnia a ra d I mtQ gr without sficl'i afiditiois as titanium?) columbiuni'fi'f nicwmeamfifaanmesmmny pickled to remove the scale in a pickling solution containing h drofl acid nixeg with an 931;- dizin lrea enii such as'chro'micf'acid, o'tgssi'um 2 chmrnmata'ifigaig gmnawlii potassium g per aiig'a'iiatefandfwfihii'without sglphugg acid. Such a pickling solution has been found esp cially satisfactory for use in connection with chrome steels or alloys thereof containing more than 12 'per cent of chromium, with or without nickel, and with or without such additions as titanium, coluhibifimmrmmyb'defiumfmse seminar may be used either hot or cold, and their composition may be varied to satisfy the individual case for which they are adapted to be used.

It has been found that a satisfactory pickling solution for most cases contains from 5 to 20 per cent by volume of a suitable oxidizing agent, such as chromic acid, potassium chromate, potassium dic oma r potassium permanganate, mixed with from of 1 per centtgjp peg ceptbyyolume of hyg c acid and with s u lphur ic acid 5 in armpits up tiS'TiYfier cent by volume, the remaining percentage of the solution, of course, being water. For example, if chromic acid is used as the oxidizing reagent, the pickling solution would then contain from 10 to 20 per cent by 10 volume of chromic acid, and from 1 to 10 per cent by volume of hydrofluoric acid and up to 10 per cent by volume of sulphuric acid mixed with water. The percentages of the amount of acid used,

of course, depends upon the type of scale on the 1 article to be pickled. It will be understood, of a course, that the acid concentration of the solution continuously decreases during the pickling operation, thereby decreasing the relative initial amounts of the ingredients of the acids used; 20 therefore the concentration of the solution has to be increased by replenishing acid from time to time.

STEPHEN F. URBAN.

Such a solution will effectively and efliciently 

